The present invention relates to a self-propelled forage harvester. Every self-propelled forage harvester is built on a ground drive, which is composed of a machine frame. The machine frame serves as a carrier for individual components. The location of the components on the machine frame plays an essential role in terms of the efficiency of the forage harvester. The components located underneath the frame are the front axle and the rear axle, each of which includes wheels. The drive wheels, wheel gears, and a transmission are installed on the front axle. The steering wheels are installed on the rear axle. Together with the front wheels, the rear axle supports the frame on the ground. The upper components are installed above the frame, i.e., the driver's cab, machine housing, and devices for processing and conveying the crop material, and the drive unit, which is supported on the machine frame. One or more containers for storing a combustible fluid are located between the frame. The location of the components relative to each other determines the weight distribution and, therefore, the center of gravity of the forage harvester. The center of gravity is also determined by the front attachment, which is located in front of the front axle, and it influences the permissible axle load.
Self-propelled agricultural harvesting machines, in particular forage harvesters and combine harvesters with a large overall mass, a heavy front attachment, and a rigid axle are adequately known from the related art. The center of gravity is determined by the design. When different front attachments are used, e.g., a combine harvester header, a corn header, or a pick-up, the center of gravity may shift, which is unfavorable.
To solve this problem, publication DD 75 665 discloses a ground drive for a forage harvester that is composed of three independent subassemblies. The assemblies are a frame, a drive axle, and a steering axle, which are interconnected via detachable connecting elements. By displacing the connecting elements, it is possible to displace the three subassemblies, thereby making it possible to shift the center of gravity of the machine.
In contrast, publication EP 1 151 655 A1 provides that all components of the harvesting machine are located relative to each other such that the center of gravity of the ready-to-operate harvesting machine with the front attachment installed is located at an exactly defined distance behind the front axle and at an exactly defined height above the ground.
The designs described in publications DD 75 665 and EP 1 151 655 A1 have the disadvantage, however, that a complex design is required in order to realize an optimal center of gravity of the machine. When front attachments are replaced often, it is therefore necessary to install additional ballast weights or to displace the connecting elements in order to optimize the center of gravity of the harvesting machine and, therefore, to control the vehicle. Harvesting machines of this type are capable of reaching driving speeds of up to 40 km/h on the road. Due to the high overall mass of the harvesting machine itself and the front attachment that is installed, it is not possible to drive the harvesting machine on the road with good control without additional ballast weights.